When working with a mobile application, that is, a program application running on a mobile device, it is desirable that the user may continue working with the application even when disconnected from the network. In such a situation, the end-to-end connection between device and central (wireline) system infrastructure is not available, due to a disruption on the unreliable wireless network component of the connection. In consequence, those applications are best built using a MOM (message oriented middleware) technology that combines client layers and a dedicated wireless gateway proxy that cooperate to shield mobile applications from wireless connection loss. Such MOM components use store and forward, session maintenance and sliding window to ensure reliable message delivery and client session integrity.
Messaging is a model in which applications are loosely coupled through the exchange of self-describing messages. This may be likened to “e-mail for applications”. Messaging allows producer applications to send messages to consumer applications, in a reliable and scalable manner. The messaging system decouples producers and consumers. It is in charge of transporting and storing messages. “Producer” and “Consumer” are just roles an application can play. An application can be both producer and consumer simultaneously, or switch roles dynamically at run-time. Two typical communication models implemented by a message system such as the commonly known JMS (Java Messaging System) are “Publish/Subscribe”, and “Point to Point messaging”.
An approach taken by Softwired Inc., with its MOM technology, iBus//Mobile and iBus//MessageServer products is to use Java and/or C# technology to extend connectivity straight through from the mobile devices to the centralized application servers. Customized applications are deployed on the mobile device, and on the server computers, using standards-based Java messaging middleware technology. A wireless data network such as GPRS, EDGE, UMTS, Mobitex, and future Wireless Broadband ‘4G’ is used to connect the mobile devices to the servers in a flexible and scalable manner.
The iBus//Mobile product defines a protocol between a mobile client layer, and a wireless proxy gateway. The mobile layer makes a JMS based API available to mobile applications, and propagates client application operations on that API across wireless networks (e.g. GSM, GPRS, UMTS) to the proxy using the protocol. Based on protocol messages received in packets across the wireless network, the gateway process is able to reflect/reproduce the mobile client operations (to the mobile API) on a proxy JMS connection between the gateway and the central messaging infrastructure. The gateway maintains this central JMS connection on behalf of the mobile client.
Such a Wireless JMS (WJMS) deployment consists of Java-enabled and non Java mobile devices (PDAs, Communicators, JavaPhones, .Net Compact Framework devices etc.) with a WJMS client library installed. The devices use a wireless network to communicate with a WJMS gateway service. The gateway is a software component capable of receiving WJMS messages from a wireless network, and of relaying these messages to a server-side JMS provider. The JMS provider either is a stand-alone JMS messaging server such as Softwired's iBus//MessageServer product, or a compliant J2EE application server such as IBM Websphere, Oracle Application Server, BEA's WebLogic Server, SAP Web Application Server or JBoss Application Server product, which should contain a JMS layer. Such a Wireless JMS (WJMS) deployment consists of programmable mobile devices (PDAs, Communicators, JavaPhones, etc.) with the WJMS client layer installed. The devices use a wireless network to communicate with a WJMS gateway service. Provided the WJMS client layer that is compatible with the mobile platform such as JavaME, Java configurations CLDC, CDC (targeting profiles such as MIDP and IMP, .Net Compact Framework (C#)) is available, client applications can be deployed to various mobile environments (e.g. Linux, RIM Blackberry, Palm, Symbian, Windows CE etc).
Softwired's U.S. Pat. No. 6,877,023 “Messaging system for delivering data in the form of portable message formats between message clients” and U.S. Pat No. 6,721,779 “Messaging proxy system” disclose mechanisms for transporting the higher level WJMS messages over the wireless link while hiding the underlying communication layer. US patent applications US 20020120717 and 20030009511, disclose a message system for delivering data in the form of messages between message clients, the system comprising a server cluster with a group of client manager nodes and a group of independent message manager nodes. The client manager nodes have the function of managing client connections, whereas the message managers are configured to store and distribute messages.
With a large number of clients distributed over a large geographic area, and in order to ensure reliability, it is necessary to distribute the functionality of the gateway process, i.e. the interface between the wireless and the wirebound part of communications, over a number of geographically separated computers. A number of separate gateway processes may run on a single computer, or distributed over several physically separate computers.